This invention relates to a process for preparing spherical carbon particles or spherical activated carbon particles from pitch or heavy oil, particularly those with a low softening point, or one below 150.degree. C.
Heretofore, pitch-based spherical carbon particles or spherical activated carbon particles have been produced by using pitch having a higher softening point than the oxidization starting temperature (usually above 150.degree. C.), shaping the pitch material into spherical particles, oxidizing said particles for infusibilizing same, and then carbonizing or activating the spherical particles.
However, pitch with a softening point of over 150.degree. C. is of a special sort and usually not available commercially, so that such pitch is difficult to obtain and hence very expensive in comparison with ordinary commercial pitch. It is therefore unremunerative to produce spherical carbon particles or spherical activated carbon particles from such pitch.
The softening point of commercially available pitch is on the order of 40.degree. to 80.degree. C. while that of heavy oil (which means residue in refining petroleum such as asphalts, tars and oils of high boiling point, hereinafter) is usually not higher than 150.degree. C. Such generally accessible pitch or heavy oil, therefore, is too low in softening point to serve immediately as material for the production of spherical carbon particles or spherical activated carbon particles.
Coal type pitch also causes difficulties in use as base material for activated carbon because spherical carbon particles prepared therefrom tend to develop cracks owing to high spherulitifying tendency of such pitch and also because the produced carbon is hard to activate.
This invention has been devised with the object of solving these problems in the prior art, and it is intended to provide a process which is capable of advantageously producing spherical carbon particles or spherical activated carbon particles by using the commercially available coal pitch or petroleum pitch with low softening point.
Other objects of this invention will become apparent from a review of the following detailed description of the invention.